Troubleshooting computer power issues can be difficult, as the problem could originate with the power supply unit, or PSU, or the motherboard. Testing each component separately helps narrow down where the problem lies. Although PSUs are designed to only work while connected to a motherboard, you can bypass this by using a small length of wire. Commonly known as the paper clip test, this shortcut offers you the ability to check that the PSU is receiving power without using the motherboard.
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1.
Disconnect the PSU from your motherboard and the wall outlet, and remove it from the computer case. The paper clip test essentially routes power through the PSU, and if the wire touches another component inside the computer during the test, it can cause a component-killing short. Move the PSU away from the rest of your computer to prevent damage.
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2.
Identify the green and black wires on the motherboard connector of the PSU. ATX power supplies offer 20- or 24-pin connectors with colored wires. The green wire is the live feed from the power cable, and the black wires are the ground wires. There is only one green wire surrounded by a number of black. It doesn't matter which black wire you choose, as they're all ground circuits.
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3.
Shape your wire for the test. Unbend your paper clip until it resembles the letter "U," or cut a short length of insulated wire and strip the ends bare. If using a paper clip, wrap some electrical tape around where the "U" curves to give yourself a safe place to hold it.
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4.
Insert one end of the wire into the green pin connector and the other end into the black. The PSU should still be unplugged from the wall and any power switch on the unit itself should be turned to “Off.” Make sure the wire is securely in place.
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5.
Plug the PSU in and flip the power switch to “On.” You should hear the internal fan start up as soon as power flows into the unit. Do not go through a surge protector or other extension cord during the test -- plug straight into the wall outlet. If you do not hear the internal fan, your PSU may have failed and you'll need to replace it. Turn off the PSU and unplug it from the wall outlet before removing the wire.
